The popularity of unvented cylinders is growing – but what are they?

In a traditional house the hot water is provided by a boiler heating a copper cylinder usually located in the airing cupboard. The hot water drains out of the copper cylinder when the hot tap is opened and there is a cold water tank in the loft which refills the copper cylinder to be reheated the next time the boiler is set to come on. In essence the hot water is fed to the taps by gravity. Many people moved away from these systems to a “combi” boiler, which is a boiler that combines the task of heating the house via the radiators and instantaneously heating the cold water into hot water via a heat exchanger. The downside of a “comb” is that it will only produce enough hot water for 1 shower (about 15 litres per minute) and so are not appropriate for a large house with 2 or 3 bathrooms.

An unvented cylinder is one where there is no tank in the loft but the supply water comes from the water main via the stop cock under the kitchen sink. This is different because, in most houses, it means these is an unlimited amount of high pressure water ready to refill the stainless steel cylinder. The higher pressures mean that the cylinder needs to be constructed to a higher strength and various safety devices need to be fitted to stop the cylinder become over pressurised, when it gets hot, which could be dangerous. Because of the safety implications these cylinders can only be installed by G3 approved installers, who have been through the appropriate training, which we are at Macoun. As a result of the higher pressure water, an unvented cylinder can supply up to 150 litres of water a minute at 45^oC, but in most domestic cases can easily supply 3 showers running at the same time.

As a safety precaution, to qualify for the manufacturers warranty and to ensure the system runs at optimum performance, the unvented cylinder requires annual servicing. This entails checking the safety devices, cleaning out the cold water filter and repressurising the expansion vessels, as well as general checks on leaks and the condition of the installation.

High pressure water without an unvented cylinder?

If you would like high pressure hot water in large quantities but without the safety issues of an unvented cylinder or you live in a flat where you are unable to discharge the safety pipework outside, then you can fit a thermal store which heats the incoming cold water via a heat exchanger.

One such excellent system is the Glenhill PulsaCoil ECO Stainless. This particular one works with off peak electricity but can be connected to the boiler. The cylinder is a thermal store and so has a large quantity of hot water which passes its heat onto the incoming cold water via a very efficient plate heat exchanger. The cylinder itself is not under high pressure and so does not need the safety devices and in fact this does not even need an overflow pipe. Therefore ideal for flats and apartment blocks.

As ever, Macoun are fully qualified to supply, fit and maintain these excellent devices, if you are considering one then please give us a call for a chat.